Cellular phones have become a major means of communication, in both the private and the business sectors. Almost all cell-phone subscribers use a car speaker-phone or a mobile speaker-phone with an earphone, to facilitate cell-phone communication while performing other tasks, including also driving. To-date, even state of the art speaker-phones detect and transmit not only the user's voice (which is what they are designed to do), but also background noises, such as traffic noises (busses, cars), engine noises, air-conditioner noises, and sometimes even just pieces of background conversations (especially while using the cell-phone in a restaurant or in a car). These background noises are amplified and transmitted in the cellular communication system. In many cases, these undesired noises overwhelm the system to a degree that the transmitted voice of the speaker is unrecognizable anymore. Furthermore, background noises occupy an unnecessary fraction of the bandwidth of the transmitted information. As internet applications become incorporated in cellular phone technology, bandwidth will become essential and increasingly expensive. For all of these reasons, it will be of a major importance if one could construct a speaker-phone/earphone system that will be somehow shielded from background noises.
Bone conduction and in particular the human skull is known to be transmitting very efficiently sound waves generated within the skull (that is the voice of that human). Several attempts were made at utilizing this phenomenon for noise reduction.
In U.S. Pat. No. 5,228,092 (Nakamura et al.) a voice transducer is disclosed, used for telecommunication by a telephone installed in a motor vehicle or the like, including: a main body having a side surface to be contacted with an operator's head so as to detect vibrations of produced voice waves when they are transmitted through the skull of the head, and convert them into electric signals; a holder member of the main body; and a connecting member which connects the main body to the holder member in such a manner that the position of the side surface of the main body with respect to the operator's head can be adjusted. The main body includes a piezoelectric transducer to detect the vibrations, a damper material which surrounds the piezoelectric transducer, and a casing which surrounds the damper material and includes the side surface to be contacted with the operator's head, and the side surface of the casing is pre-treated to have a small coefficient of friction. The proposed transducer aims at solving problems of output voltage drop and drastic deterioration of the S/N ratio which are induced by unfavorable contact between the voice transducer and the operator's head or by unnecessary vibrations which are generated by friction between the operator's hair and the voice transducer.
U.S. Pat. No. 6,408,081 (Boesen) discloses a voice sound transmitting unit having an earpiece that is adapted for insertion into the external auditory canal of a user, the earpiece having both a bone conduction sensor and an air conduction sensor. The bone conduction sensor is adapted to contact a portion of the external auditory canal to convert bone vibrations of voice sound information into electrical signals. The air conduction sensor resides within the auditory canal and converts air vibrations of the voice sound information into electrical signals. In its preferred form, a speech processor samples output from the bone conduction sensor and the air conduction sensor to filter noise and select the a pure voice sound signal for transmission. The transmission of the voice sound signal may be through a wireless linkage and may also be equipped with a speaker and receiver to enable two-way communication.
U.S. Pat. No. 6,668,065 (Lee et al.) discloses a bone-conduction transducer comprising a plate-shaped yoke bent to form a pair of cut portions at both ends thereof; voice coils fitted to a center extension of the cut portions; a magnet and a plate of rectangular parallelepiped shape disposed between the voice coils; and a diaphragm minutely spaced from a lower part of the plate.
Other bone-conduction devices are disclosed in U.S. Pat. No. 6,463,157, U.S. Pat. No. 6,104,816, U.S. Pat. No. 5,757,934, U.S. Pat. No. 5,327,506.
It is an object of the present invention to provide a novel transducer that utilizes the bone-conduction phenomenon.
Another object of the present invention is to provide such transducer that employs optical means (with no need for acoustic detection) to detect the audio signal conducted through the skull of a person talking into his telecommunication device (in particular, but not only, cellular phone).
Another object of the present invention is to use optical means to detect audio signals generated in the human body, such as heart beats, sounds generated in the lungs, and blood flow.
Yet another object of the present invention is to provide a shielded communication device that can be used to detect and enhance sounds originating from within any body that has an acoustically excitable surface, and ignore or greatly reduce background noises.